Help with over-fuelling TDV8

[Krikkit]

Problem with my L322 - parked it up one night fine, next day the right bank of the engine is spewing fuel smoke (it's white, persistent and stinks of diesel). Coolant level is unchanged and fine, oil level fine so I've ruled out a head gasket failure. Left bank of the engine is completely fine and smoke-free, so ruled out bad fuel or other global catastrophes.

I spotted a very slight crack in the cam cover/inlet on the smoking side, replaced it and no change (I wasn't really expecting it to be fixed but needed doing). Turbo replaced with a recon and no different. 4x replacement injectors fitted and no difference. I have swapped the MAF, MAP and throttles between sides with no difference.

There are now no visible leaks of any kind anywhere in the top end. The inlet isn't full of oil or anything to indicate a bad oil seal.

Reading the various sensor data with my laptop, I have:

• MAF reading on the smoky side is very high, roughly 10x higher than the good side (6kg/hr vs 60kg/hr), and the airflow from the airbox feels correct (the smoky side is drawing a lot more air)
• EGR values the same to both sides (both commanded and actual), EGRs were new in October
• Throttles are moving and the same values both sides
• Turbo actuator is free and operating correctly
• MAP sensor reading about the same for both sides
• Intercooler outlet temperature for the smoky side is much higher
• Checked the wiring loom back to the ECU from the injectors, no funny cross-overs or anything
• No stored trouble codes

Any ideas? My current thinking is the ECU has somehow failed, as all the mechanical causes seem to be resolved.

Edit: finally sorted a video

https://youtu.be/UL-Uw-VvpPE

Edited by Krikkit on Tuesday 25th July 21:44

[Krikkit]

Said smoky side, it's actually more pronounced than it looks here.

[Bigmanmike.]

My car did that when egr valve was blocked. Egr replaced and fixed bro. Could be glow plugs too happened with me. u prob don't have egr because its so old? Mine didn't have any codes either untill 8k miles later for egr

Edited by Bigmanmike. on Friday 14th July 06:52

Edited by Bigmanmike. on Friday 14th July 06:54

Edited by Bigmanmike. on Friday 14th July 08:24

[E-bmw]

Bigmanmike. said:

Could be coils too happened with me.

It's a diesel.

[Bigmanmike.]

E-bmw said:

Bigmanmike. said:

Could be coils too happened with me.

It's a diesel.

Glow plugs I meant

[Krikkit]

Bigmanmike. said:

My car did that when egr valve was blocked. Egr replaced and fixed bro. Could be glow plugs too happened with me. u prob don't have egr because its so old? Mine didn't have any codes either untill 8k miles later for egr

EGR working as it should and not blocked, glow plugs not relevant as it doesn't change if warmed up for a few minutes (and it's way, way more fuel than normal)

[Peanut Gallery]

Could an injector have failed open? - How hard to test the residual pressure in a fuel rail on either side, does the pressure drop faster on the smokey side when engine is turned off - or is there one cylinder that the exhaust is cooler than the other 3, meaning that cylinder has not woken up?

The fact the air flow meter thinks 10 times more air is going in, the ECU could be trying to dump 10 times more fuel into that side - if you swopped the leads to the air flow sensors over (or swopped the MAFs over), does the ECU then over-fuel the other bank?

[Krikkit]

Peanut Gallery said:

Could an injector have failed open? - How hard to test the residual pressure in a fuel rail on either side, does the pressure drop faster on the smokey side when engine is turned off - or is there one cylinder that the exhaust is cooler than the other 3, meaning that cylinder has not woken up?

The symptoms are as if they're all wide open - unplug one injector and it marginally improves, but nothing significant. Can't get to the exhaust manifold while it's running as it's buried too deep.

I've swapped all 4 for used replacements, taken from a running lump that I've no reason to think was broken.

Peanut Gallery said:

The fact the air flow meter thinks 10 times more air is going in, the ECU could be trying to dump 10 times more fuel into that side - if you swopped the leads to the air flow sensors over (or swopped the MAFs over), does the ECU then over-fuel the other bank?

I've both swapped the MAFs (no change) and tried to trick the ECU by plugging in the smoking side to the one on the OK side, no change. Unfortunately I initially couldn't decide whether it was chicken or egg, whether it was the turbo stuck in maximum boost pulling extra air (and therefore more fuel to correct it) or the opposite way.

[Megaflow]

This is an out there idea... but I wonder if there is an air leak and all the excess air being pulled through the MAF is going to atmosphere not to the engine. The engine thinks it is putting in enough fuel to deal with all the air, but the air isn't there, so it can't burn the fuel, hence why it comes out the back unburnt.

Just a thought.

[Krikkit]

Megaflow said:

This is an out there idea... but I wonder if there is an air leak and all the excess air being pulled through the MAF is going to atmosphere not to the engine. The engine thinks it is putting in enough fuel to deal with all the air, but the air isn't there, so it can't burn the fuel, hence why it comes out the back unburnt.

Just a thought.

Thanks it's a good thought indeed - the inlet on the smoking side is full of smoke too (EGR recycle presumably), so it's effectively its own smoke tester. Unless the intercooler has popped between the two sets of cylinders, and it's then going into the "good" half and being combusted, there's no leaks.

[coetzeeh]

when last were the turbo inlet pipes replaced?

I noticed excessive smoking on one side of my TDV8 recently and local Indie found a split one side - did not show any error codes.

[Belle427]

I'd agree about investigating the Maf reading, doesn't make sense.

[Megaflow]

Krikkit said:

Thanks it's a good thought indeed - the inlet on the smoking side is full of smoke too (EGR recycle presumably), so it's effectively its own smoke tester. Unless the intercooler has popped between the two sets of cylinders, and it's then going into the "good" half and being combusted, there's no leaks.

I said it was an out there idea, because normally an air leak would mean unmetered air making its way into the engine, not the other way around.

Just for the sake of clarity, when you swap the MAF’s between banks, it is still the same bank with a massive mass flow reading, correct?

[Krikkit]

Megaflow said:

Just for the sake of clarity, when you swap the MAF’s between banks, it is still the same bank with a massive mass flow reading, correct?

Correct, the faulty side always shows the high reading.

From the highly scientific holding your hand next to the airbox outlet, the MAF reading is correct - the smoking bank is drawing a massive doubt more air than the ok side.

[Krikkit]

coetzeeh said:

when last were the turbo inlet pipes replaced?

I noticed excessive smoking on one side of my TDV8 recently and local Indie found a split one side - did not show any error codes.

I've no idea, but I've checked them and they're not leaking (either the large plastic inlet pipe, the aluminium outlet pipe to the intercooler, or the intercooler to inlet manifold pipe)

[Peanut Gallery]

Krikkit said:

Correct, the faulty side always shows the high reading.

From the highly scientific holding your hand next to the airbox outlet, the MAF reading is correct - the smoking bank is drawing a massive doubt more air than the ok side.

That air must be going somewhere, I am guessing!!

Do you have access to a small air generating device, or even better a smoke machine? - blow air into that inlet, and look for where it is coming out? - My money is more and more on that MAF telling the ECU there is a ton of air coming in, dump more fuel now!

[Krikkit]

Peanut Gallery said:

That air must be going somewhere, I am guessing!!

Do you have access to a small air generating device, or even better a smoke machine? - blow air into that inlet, and look for where it is coming out? - My money is more and more on that MAF telling the ECU there is a ton of air coming in, dump more fuel now!

There's no leaks - the high fuel content means that the air inside the inlet is effectively a smoke machine of its own, remove an inlet pipe 10 minutes after the engine is off and it's still full of smoke.

[Peanut Gallery]

What confuses me is that you say the smokey side is sucking more air in than the non smokey side? - in both the technical feel air rush past hand and according to the MAF?

[Megaflow]

Krikkit said:

Megaflow said:

Just for the sake of clarity, when you swap the MAF’s between banks, it is still the same bank with a massive mass flow reading, correct?

Correct, the faulty side always shows the high reading.

From the highly scientific holding your hand next to the airbox outlet, the MAF reading is correct - the smoking bank is drawing a massive doubt more air than the ok side.

Interesting. No, it is not a scientific test at all, but given the scale of the numbers involve, it does actually physically confirm the the right hand bank is indeed sucking in more air than the left hand bank.

The ECU is going to inject fuel based on that number, and judging by the grey smoke and unburnt diesel coming out of the back, that air is not making it to the cylinder to burn with the fuel. Very curious.

Have you done a compression test?

Krikkit said:

There's no leaks - the high fuel content means that the air inside the inlet is effectively a smoke machine of its own, remove an inlet pipe 10 minutes after the engine is off and it's still full of smoke.

This comment is interesting. Are you saying the inlet manifold is still full of smoke are turning off? If so, there shouldn't be smoke in the inlet and it sounds like it is stuck in the inlet.

Have you got any error messages when you scan it?

Edited by Megaflow on Tuesday 18th July 12:21

[Krikkit]

Megaflow said:

The ECU is going to inject fuel based on that number, and judging by the grey smoke and unburnt diesel coming out of the back, that air is not making it to the cylinder to burn with the fuel. Very curious.

Indeed, and is why I originally went down the route of the turbo being stuck in maximum boost configuration originally. But then if that all seems normal, could it be the opposite way?

Megaflow said:

Have you done a compression test?

No, but it ran perfectly the night before the issue started, I did about 80 miles in it with no noticeable issues. I don't have the kit for a diesel comp test.

Megaflow said:

Krikkit said:

There's no leaks - the high fuel content means that the air inside the inlet is effectively a smoke machine of its own, remove an inlet pipe 10 minutes after the engine is off and it's still full of smoke.

This comment is interesting. Are you saying the inlet manifold is still full of smoke are turning off? If so, there shouldn't be smoke in the inlet and it sounds like it is stuck in the inlet.

The EGR is position is running 5-10% from a cold start, so I'd expect the fuel-rich smoke to be cycled back through, it's thinner than the exhaust.

Megaflow said:

Have you got any error messages when you scan it?

Nothing logged.